Apr 30, 2009 - Abstract. Background The repeatability and interchangeability of imaging devices measuring central corneal thickness. (CCT) and anterior ...
Graefes Arch Clin Exp Ophthalmol (2009) 247:1139–1146 DOI 10.1007/s00417-009-1086-6
REFRACTIVE SURGERY
Comparison of central corneal thickness and anterior chamber depth measurements using three imaging technologies in normal eyes and after phakic intraocular lens implantation Muriël Doors & Lars P. J. Cruysberg & Tos T. J. M. Berendschot & John de Brabander & Frenne Verbakel & Carroll A. B. Webers & Rudy M. M. A. Nuijts
Received: 24 October 2008 / Revised: 23 March 2009 / Accepted: 6 April 2009 / Published online: 30 April 2009 # The Author(s) 2009. This article is published with open access at Springerlink.com
Abstract Background The repeatability and interchangeability of imaging devices measuring central corneal thickness (CCT) and anterior chamber depth (ACD) are important in the assessment of patients considering refractive surgery. The purpose of this study was to investigate the agreement of CCT and ACD measurements using three imaging technologies in healthy eyes and in eyes after phakic intraocular lens implantation (pIOL). Methods In this comparative study, CCT and ACD were measured using anterior segment optical coherence tomography (AS-OCT), Orbscan II, and Pentacam in 33 healthy volunteers (66 eyes) and 22 patients (42 eyes) after pIOL implantation. Intraobserver repeatability was evaluated for all three devices in the healthy volunteer group. Results Pairwise comparison of CCT measurements showed significant differences between all devices (P90% for both groups to detect a 15-μm difference between two measurement methods. For within-subject ACD measurements, a SD ranging from 0.001 to 0.052 mm for Orbscan, Pentacam and AS-OCT has been described [11, 18]. Thus, with a significance level of 0.05, our study with 66 healthy eyes and 42 pIOL eyes has a power of >90% for both groups to detect a 0.10 mm difference between two measurement methods. All data were collected in an Excel database and transferred to SPSS (SPSS for Windows, version 15.0, SPSS Inc, Chicago, IL, USA) for data analysis. Continuous variables were described as mean±SD. Paired t-tests were applied to compare CCT and ACD measurements between two applications in the healthy volunteer group and the pIOL group. To determine a relationship between the measurements of two devices, the Pearson’s correlation coefficient (r) was used. The agreement between two devices was studied using the method described by Bland and Altman [19]. This method also computed 95% limits of agreement (LoA=mean difference ± 1.96 SD). To determine intraobserver reliability between three consecutive measurements in the healthy volunteer group, the mean standard deviation between three consecutive measurements (SDwithin), the coefficient of variation (CV) (ratio of SDwithin and mean in percentage), and precision (1.96 * SDwithin) were calculated. A P-value of
